Geospace Exploration by the ERG mission

Editorial Board (October 2019)
Editor-in-Chief
Yasuo Ogawa, Tokyo Institute of Technology, Japan

Vice Editors-in-Chief
Masato Furuya, Hokkaido University, Japan
Solid Earth Science

Nozomu Nishitani, Nagoya University, Japan
Space Science

Editors
Valerio Acocella
Ryosuke Ando
Kimiyuki Asano
Nanan Balan
Paul Bedrosian
Phil Cummins
Hao Dong
Koji Fukuma
Shin-Chan Han
James Hickey
Thomas Hobiger
Hauke Hussmann
Takeo Ito
Art Jolly
Tomokazu Kobayashi
Attila Komjathy

Alexey Kuvshinov
Juanjo Ledo
Huixin Liu
Yohei Miyake
Mitsuhiro Nakagawa
Junichi Nakajima
Haruhisa Nakamichi
Yasuhito Narita
Takuya Nishimura
Takaaki Noguchi
Masahito Nose
Makiko Ohtake
Keiji Ohtsuki
Kyoko Okino
Duggirala Pallamraju
Severine Rosat

Akinori Saito
Tatsuhiko Saito
David Shelly
Hiroko Sugioka
Benoit Taisne
Sunny TamYoshiyuki Tanaka
Yanbin Wang
Yih-Min Wu
Chuang Xuan
Takuji Yamada
Mare Yamamoto
Tadashi Yamasaki
Tatsuhiro Yokoyama
Kazunori Yoshizawa

Hiroo Kanamori
Jun'ichiro Kawaguchi
Takafumi Matsui
Hitoshi Mizutani

Toshitaka Tsuda
Zhongliang Wu
Kiyoshi Yomogida

Advisory Board
Benjamin Fong Chao
Bernard Chouet
Yoshimori Honkura
Toshihiko Iyemori

Journal Scope
Earth, Planets and Space (EPS) is the official journal of the Society of Geomagnetism and Earth, Planetary
and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan, The
Geodetic Society of Japan, and The Japanese Society for Planetary Sciences.
EPS is a peer-reviewed, open-access journal published under SpringerOpen. It is an international journal
covering scientific articles in the entire field of earth and planetary sciences, particularly geomagnetism,aeronomy, space science, seismology, volcanology, geodesy, and planetary science. EPS also welcomesarticles in new and interdisciplinary subjects, and technical reports on instrumentation and software.
The journal was launched in 1998 and has since published over 3000 articles. All of them are available forfree on SpringerLink:
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Editor-in-Chief, Earth, Planets and Space
editor-in-chief@earth-planets-space.org

Earth, Planets and Space
Nagai et al. Earth, Planets and Space (2018) 70:155
https://doi.org/10.1186/s40623-018-0926-1

Open Access

PREFACESpecial issue “Geospace Explorationby the ERG mission”
Tsugunobu Nagai1*, Barry Mauk2, Ondrej Santolik3,4, Takashi Kubota1 and Takeshi Sakanoi5

by Shiokawa et al. (2017). Other key aspects of the ERG
project are a program of theory, modeling, and integrating studies described by Seki et al. (2018), and a data processing center called the ERG Science Center, describedby Miyoshi et al. (2018b). An example of the data analysis
tool development is introduced by Keika et al. (2017). Allof these elements together are expected to yield majoradvancements in our understanding of acceleration,transport, and loss of relativistic electrons in the radiation belts.

The exploration of energization and radiation in geospace(ERG) project was developed to understand the fundamental physical processes operating in the Earth’s innermagnetosphere. A summary of the ERG project is givenin this special issue by Miyoshi et al. (2018a). A centralcomponent of this project is the spacecraft Arase, named
after the Arase River near the ISAS launch range, (ERG).
Arase was launched on December 20, 2016, and it has
been operating in a highly elliptical orbit with apogeeof 6 RE and an inclination of 31°. A brief history of thespacecraft development and the technical features of thespacecraft system are given by Nakamura et al. (2018).
The spacecraft has an innovated mission network systemdescribed by Takashima et al. (2018). Arase hosts ninestate-of-the-art scientific instruments to make in situ
observations of particles and fields. The multiple instruments for electron measurements are introduced byKazama et al. (2017), Kasahara et al. (2018a, b), Mitani
et al. (2018), and Higashio et al. (2018). The instruments
for ion measurements are introduced by Asamura et al.
(2018) and Yokota et al. (2017). The magnetic field measurements are described by Matsuoka et al. (2018), anddescriptions of the wave and electric fields are provided
by Kasahara et al. (2018a, b), Kasaba et al. (2017), Kumamoto et al. (2018), Ozaki et al. (2018), and Matsuda et al.
(2018). The interactions between particles and waves,
a critical aspect of the physics of the inner magnetosphere, are diagnosed with a software-type wave-particle
interaction analyzer, introduced by Katoh et al. (2018)
and Hikishima et al. (2018). The ERG project includes aground-based observation network that is summarized

Authors’ contributions
All authors of this article served as guest editors for this special issue. All
authors read and approved the final manuscript.
Author details
1
Institute of Space and Astronautical Science (ISAS), Japan Aerospace Explora‑tion Agency (JAXA), 3‑1‑1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252‑5210,
Japan. 2 Applied Physics Laboratory, The Johns Hopkins University, Laurel,
MD, USA. 3 Department of Space Physics, Institute of Atmospheric Physics,
The Czech Academy of Sciences, Prague, Czechia. 4 Faculty of Mathematics
and Physics, Charles University, Prague, Czechia. 5 Graduate School of Science,
Tohoku University, 6‑3 Aramaki aza aoba, Aoba ku, Sendai 980‑8578, Japan.
Competing interests
The authors declare that they have no competing interests.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims in pub‑lished maps and institutional affiliations.
Received: 14 September 2018 Accepted: 15 September 2018

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1

Geospace Exploration by the ERG mission
Nagai et al. Earth, Planets and Space (2018) 70:155

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K, Shibano Y (2017) Medium‑energy particle experiments‑ion mass
analyzer (MEP‑i) onboard ERG (Arase). Earth Planets Space 69:172. https://doi.org/10.1186/s40623‑017‑0754‑82Earth, Planets and Space

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Open Access

Ground-based instruments of the PWING project to investigate dynamics
of the inner magnetosphere at subauroral latitudes as a part of the
ERG-ground coordinated observation network
Kazuo Shiokawa*, Yasuo Katoh, Yoshiyuki Hamaguchi, Yuka Yamamoto, Takumi Adachi, Mitsunori Ozaki, Shin‑Ichiro Oyama, Masahito Nosé,
Tsutomu Nagatsuma, Yoshimasa Tanaka, Yuichi Otsuka, Yoshizumi Miyoshi, Ryuho Kataoka, Yuki Takagi, Yuhei Takeshita, Atsuki Shinbori,Satoshi Kurita, Tomoaki Hori, Nozomu Nishitani, Iku Shinohara, Fuminori Tsuchiya, Yuki Obana, Shin Suzuki, Naoko Takahashi,
Kanako Seki, Akira Kadokura, Keisuke Hosokawa, Yasunobu Ogawa, Martin Connors, J. Michael Ruohoniemi, Mark Engebretson,
Esa Turunen, Thomas Ulich, Jyrki Manninen, Tero Raita, Antti Kero, Arto Oksanen, Marko Back, Kirsti Kauristie, Jyrki Mattanen,
Dmitry Baishev, Vladimir Kurkin, Alexey Oinats, Alexander Pashinin, Roman Vasilyev, Ravil Rakhmatulin, William Bristow and Marty Karjala
Earth, Planets and Space 2017, 69:160 DOI:10.1186/s40623-017-0745-9
Received: 4 September 2017, Accepted: 14 November 2017, Published: 28 November 2017

Abstract
The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to mega-electron volts (MeV). These plasmas rotate
around the Earth longitudinally due to the gradient and curvature of the geomagnetic field and by the co-rotation motion with timescales from several tens of hours
to less than 10 min. They interact with plasma waves at frequencies of mHz to kHz mainly in the equatorial plane of the magnetosphere, obtain energies up to MeV,
and are lost into the ionosphere. In order to provide the global distribution and quantitative evaluation of the dynamical variation of these plasmas and waves in the
inner magnetosphere, the PWING project (study of dynamical variation of particles and waves in the inner magnetosphereusing ground-based network observations, http://www.isee.nagoya-u.ac.jp/dimr/PWING/) has been carried out since ApriloParatunka
60
2016. This paper describes the stations and instrumentation of the PWING project. We operate all-sky airglow/aurora imagers,
Athabasca
64-Hz sampling induction magnetometers, 40-kHz sampling loop antennas, and 64-Hz sampling riometers at eight stations at
Gakona70
Magadansubauroral latitudes (~ 60° geomagnetic latitude) in the northern hemisphere, as well as 100-Hz sampling EMCCD cameras at80
three stations. These stations are distributed longitudinally in Canada, Iceland, Finland, Russia, and Alaska to obtain the
Zhigansk
longitudinal distribution of plasmas and waves in the inner magnetosphere. This PWING longitudinal network has been
Resolute
Kapuskasing
Eurekadeveloped as a part of the ERG (Arase)-ground coordinated observation network. The ERG (Arase) satellite was launched on
Istok
December 20, 2016, and has been in full operation since March 2017. We will combine these ground network observations withKevo
the ERG (Arase) satellite and global modeling studies. These comprehensive datasets will contribute to the investigation of
HusafellNain
Tromsoedynamical variation of particles and waves in the inner magnetosphere, which is one of the most important research topics inrecent space physics, and the outcome of our research will improve safe and secure use of geospace around the Earth.
ooKeywords: All-sky airglow/aurora imager, Induction magnetometer, Riometer, Loop antenna, EMCCD camera,

MLAT-MLT map

NyrolaGraphical abstract

Inner magnetosphere, SAR arc, Magnetospheric ELF/VLF wave, EMIC wave, Radiation belts*Corresponding author: Kazuo Shiokawa, shiokawa@nagoya‑u.jp

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Low-energy particle experiments–electron analyzer (LEPe)
onboard the Arase spacecraft
Yoichi Kazama*, Bo-Jhou Wang, Shiang-Yu Wang, Paul T. P. Ho, Sunny W. Y. Tam, Tzu-Fang Chang,
Chih-Yu Chiang and Kazushi Asamura
Earth, Planets and Space 2017, 69:165 DOI:10.1186/s40623-017-0748-6
Received: 6 September 2017, Accepted: 19 November 2017, Published: 11 December 2017

Abstract
In this report, we describe the low-energy electron instrument LEPe (low-energy particle experiments–electron analyzer)
onboard the Arase (ERG) spacecraft. The instrument measures a three-dimensional distribution function of electrons withenergies of ~ 19 eV–19 keV. Electrons in this energy range dominate in the inner magnetosphere, and measurement of suchelectrons is important in terms of understanding the magnetospheric dynamics and wave–
particle interaction. The instrument employs a toroidal tophat electrostatic energy analyzer
with a passive 6-mm aluminum shield. To minimize background radiation effects, theanalyzer has a background channel, which monitors counts produced by backgroundradiation. Background counts are then subtracted from measured counts. Electronic
components are radiation tolerant, and 5-mm-thick shielding of the electronics housing
ensures that the total dose is less than 100 kRad for the one-year nominal mission lifetime.
The first in-space measurement test was done on February 12, 2017, showing that the
instrument functions well. On February 27, the first all-instrument run test was done, and the
LEPe instrument measured an energy dispersion event probably related to a substorm
injection occurring immediately before the instrument turn-on. These initial results indicatethat the instrument works fine in space, and the measurement performance is good forscience purposes.

Keywords: Low-energy electron measurement, Particle instrumentation, Inner
magnetosphere

Graphical abstract*Corresponding author: Yoichi Kazama, kazama.yoichi@asiaa.sinica.edu.tw3Geospace Exploration by the ERG mission

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Open Access

Medium-energy particle experiments–ion mass analyzer (MEP-i)
onboard ERG (Arase)
Shoichiro Yokota*, Satoshi Kasahara, Takefumi Mitani, Kazushi Asamura, Masafumi Hirahara,
Takeshi Takashima, Kazuhiro Yamamoto and Yasuko Shibano
Earth, Planets and Space 2017, 69:172 DOI:10.1186/s40623-017-0754-8
Received: 30 August 2017, Accepted: 5 December 2017, Published: 21 December 2017

Abstract
The medium-energy particle experiments–ion mass analyzer (MEP-i) was
developed for the exploration of energization and radiation in geospace(ERG) mission (Arase), in order to measure the three-dimensional
distribution functions of the inner-magnetospheric ions in the medium
energy range between 10 and 180 keV/q. The energy, mass, and charge
state of each ion are determined by a combination of an electrostatic
energy/charge analyzer, a time-of-flight mass/charge analyzer, andenergy-sensitive solid-state detectors. This paper describes the
instrumentation of the MEP-i, data products, and observation results
during a magnetic storm.

a

b

i+

ESA
TOF

SSD
MCP

Keywords: ERG, Radiation belts, Medium-energy particles, MassCounts105

150

analyses

104(keV/q)

100

103

50

102
101
10

0

50
H+

100
He+

He++

150
200
O++
N+/O+
Time-of-flight (ch)250
300
N2+/NO+/O2+

100

Graphical abstract*Corresponding author: Shoichiro Yokota, yokota@ess.sci.osaka‑u.ac.jp

FULL PAPER

Open AccessWire Probe Antenna (WPT) and Electric Field Detector (EFD) of Plasma
Wave Experiment (PWE) aboard the Arase satellite: specifications andinitial evaluation results
Yasumasa Kasaba*, Keigo Ishisaka, Yoshiya Kasahara, Tomohiko Imachi, Satoshi Yagitani, Hirotsugu Kojima, Shoya Matsuda,
Masafumi Shoji, Satoshi Kurita, Tomoaki Hori, Atsuki Shinbori, Mariko Teramoto, Yoshizumi Miyoshi, Tomoko Nakagawa,
Naoko Takahashi, Yukitoshi Nishimura, Ayako Matsuoka, Atsushi Kumamoto, Fuminori Tsuchiya and Reiko Nomura
Earth, Planets and Space 2017, 69:174 DOI:10.1186/s40623-017-0760-x
Received: 9 September 2017, Accepted: 10 December 2017, Published: 27 December 2017

Abstract
This paper summarizes the specifications and initial evaluation results of Wire Probe Antenna (WPT) and Electric Field Detector (EFD), the key components forthe electric field measurement of the Plasma Wave Experiment (PWE) aboard the Arase (ERG) satellite. WPT consists of two pairs of dipole antennas with~ 31-m tip-to-tip length. Each antenna element has a spherical probe (60 mm diameter) at each end of the wire (15 m length). They are extended
orthogonally in the spin plane of the spacecraft, which is roughly perpendicular to the Sun and enables to measure the electric field in the frequency range of
DC to 10 MHz. This system is almost identical to the WPT of Plasma Wave Investigation aboard the BepiColombo Mercury Magnetospheric Orbiter, except forthe material of the spherical probe (ERG: Al alloy, MMO: Ti alloy). EFD is a part of the EWO (EFD/WFC/OFA) receiver and measures the 2-ch electric field at asampling rate of 512 Hz (dynamic range: ± 200 mV/m) and the 4-ch spacecraft potential at a sampling rate of 128 Hz (dynamic range: ± 100 V and ± 3 V/m),with the bias control capability of WPT. The electric field waveform provides (1) fundamental
WPT-S-V1
Vv1(WPT-S3)
information about the plasma dynamics and accelerations and (2) the characteristics of MHD and ion
waves in various magnetospheric statuses with the magnetic field measured by MGF and PWE–MSC.
Z
X
EvThe spacecraft potential provides information on thermal electron plasma variations and structureY
combined with the electron density obtained from the upper hybrid resonance frequency provided
Sunwardspin directionV
u2
by PWE–HFA. EFD has two data modes. The continuous (medium-mode) data are provided as (1) 2-ch
WPT-S-U2
waveforms at 64 Hz (in apoapsis mode, L > 4) or 256 Hz (in periapsis mode, L < 4), (2) 1-ch spectrum(WPT-S2)
Vu1
within 1–232 Hz with 1-s resolution, and (3) 4-ch spacecraft potential at 8 Hz. The burst (high-mode)
WPT-S-U1
data are intermittently obtained as (4) 2-ch waveforms at 512 Hz and (5) 4-ch spacecraft potential at
Eu(WPT-S1)
128 Hz and downloaded with the WFC-E/B datasets after the selection. This paper also shows theinitial evaluation results in the initial observation phase.
WPT-S-V2
SGA

SGA

SGA

Keywords: Electric field, Plasma wave, Spacecraft potential, Electron density and temperature,
Wire Probe Antenna (WPT), Electric Field Detector (EFD), Plasma Wave Experiment(PWE), Arase spacecraft*Corresponding author: Yasumasa Kasaba, kasaba@pat.gp.tohoku.ac.jp(WPT-S4)

Vv2

SunwardGraphical
abstract
Xb

SGA

WPT-S-U2

Vu2(WPT-S2)ZSGA

WPT-S-V2
YSGA(WPT-S4)

Vv2
ZSSI

4

spin direction

YSSI

XSSI

Earth, Planets and Space

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Software-type Wave–Particle Interaction Analyzer on board the Arasesatellite
Yuto Katoh*, Hirotsugu Kojima, Mitsuru Hikishima, Takeshi Takashima, Kazushi Asamura, Yoshizumi Miyoshi,
Yoshiya Kasahara, Satoshi Kasahara, Takefumi Mitani, Nana Higashio, Ayako Matsuoka, Mitsunori Ozaki,
Satoshi Yagitani, Shoichiro Yokota, Shoya Matsuda, Masahiro Kitahara and Iku Shinohara
Earth, Planets and Space 2018, 70:4 DOI:10.1186/s40623-017-0771-7
Received: 31 August 2017, Accepted: 25 December 2017, Published: 8 January 2018

Abstract
We describe the principles of the Wave–Particle Interaction Analyzer (WPIA) and the implementation of the Software-type WPIA (S-WPIA) on the
Arase satellite. The WPIA is a new type of instrument for the direct and quantitative measurement of wave–particle interactions. The S-WPIA is
installed on the Arase satellite as a software function running on the mission data processor. The S-WPIA on board the Arase satellite uses anelectromagnetic field waveform that is measured by the waveform capture receiver of the plasma wave experiment (PWE), and the velocity vectors ofelectrons detected by the medium-energy particle experiment–electron analyzer (MEP-e), the high-energy electron experiment (HEP), and theextremely high-energy electron experiment (XEP). The prime objective of the S-WPIA is to measure the energy exchange between whistler-mode
chorus emissions and energetic electrons in the inner magnetosphere. It is essential for the S-WPIA to synchronize instruments to a relative time
accuracy better than the time period of the plasma wave oscillations. Since the typical frequency of chorus emissions in the inner magnetosphere is a
few kHz, a relative time accuracy of better than 10 μs is required in order to measure
the relative phase angle between the wave and velocity vectors. In the Arasesatellite, a dedicated system has been developed to realize the time resolution
required for inter-instrument communication. Here, both the time index distributed
over all instruments through the satellite system and an S-WPIA clock signal areused, that are distributed from the PWE to the MEP-e, HEP, and XEP through a direct
line, for the synchronization of instruments within a relative time accuracy of a few
μs. We also estimate the number of particles required to obtain statisticallysignificant results with the S-WPIA and the expected accumulation time by referringto the specifications of the MEP-e and assuming a count rate for each detector.

Keywords: Radiation belts, Magnetosphere, Whistler-mode chorus,
Wave–particle interactions

Graphical abstract*Corresponding author: Yuto Katoh, yuto@stpp.gp.tohoku.ac.jp

FULL PAPER

Open Access

Theory, modeling, and integrated studies in the Arase (ERG) project
Kanako Seki*, Yoshizumi Miyoshi, Yusuke Ebihara, Yuto Katoh, Takanobu Amano, Shinji Saito,
Masafumi Shoji, Aoi Nakamizo, Kunihiro Keika, Tomoaki Hori, Shin’ya Nakano, Shigeto Watanabe,
Kei Kamiya, Naoko Takahashi, Yoshiharu Omura, Masahito Nosé, Mei-Ching Fok, Takashi Tanaka,
Akimasa Ieda and Akimasa Yoshikawa
Earth, Planets and Space 2018, 70:17 DOI:10.1186/s40623-018-0785-9
Received: 15 September 2017, Accepted: 17 January 2018, Published: 1 February 2018

Abstract
Understanding of underlying mechanisms of drastic variations of the near-Earth space (geospace) is one of the current focuses of themagnetospheric physics. The science target of the geospace research project Exploration of energization and Radiation in Geospace(ERG) is to understand the geospace variations with a focus on the relativistic electron acceleration and loss processes. In order toachieve the goal, the ERG project consists of the three parts: the Arase (ERG) satellite, ground-based observations, and theory/modeling/integrated studies. The role of theory/modeling/integrated studies part is to promote relevant theoretical and simulation
studies as well as integrated data analysis to combine different kinds of observations and modeling. Here we provide technicalreports on simulation and empirical models related to the ERG project together with their roles in the integrated studies of dynamic
geospace variations. The simulation and empirical models covered include the radial diffusion model of the radiation belt electrons,
GEMSIS-RB and RBW models, CIMI model with global MHD
simulation REPPU, GEMSIS-RC model, plasmaspherethermosphere model, self-consistent wave–particle interaction
simulations (electron hybrid code and ion hybrid code), theionospheric electric potential (GEMSIS-POT) model, andSuperDARN electric field models with data assimilation. ERG(Arase) science center tools to support integrated studies withvarious kinds of data are also briefly introduced.

Keywords: Inner magnetosphere, Numerical simulation/modeling, Geospace, Magnetic storms, Arase/ERG

Fig. 1*Corresponding author: Kanako Seki, k.seki@eps.s.u‑tokyo.ac.jp
5Fig. 11

Geospace Exploration by the ERG mission

FULL PAPER

Open Access

The ARASE (ERG) magnetic field investigation
Ayako Matsuoka*, Mariko Teramoto, Reiko Nomura, Masahito Nosé, Akiko Fujimoto,
Yoshimasa Tanaka, Manabu Shinohara, Tsutomu Nagatsuma, Kazuo Shiokawa, Yuki Obana,
Yoshizumi Miyoshi, Makoto Mita, Takeshi Takashima and Iku Shinohara
Earth, Planets and Space 2018, 70:43 DOI:10.1186/s40623-018-0800-1
Received: 20 September 2017, Accepted: 7 February 2018, Published: 14 March 2018

Abstract
The fluxgate magnetometer for the Arase (ERG) spacecraft mission was built to investigate particle acceleration processes in
the inner magnetosphere. Precise measurements of the field intensity and direction are essential in studying the motion ofparticles, the properties of waves interacting with the particles, and magnetic field variations induced by electric currents. By
observing temporal field variations, we will more deeply understand magnetohydrodynamic and electromagnetic ioncyclotron waves in the ultra-low-frequency range, which can cause production and loss of relativistic electrons and ringcurrent particles. The hardware and software designs of the Magnetic Field Experiment (MGF) were optimized to meet therequirements for studying these phenomena. The MGF makes measurements at a sampling rate of 256 vectors/s, and the data
are averaged onboard to fit the telemetry budget. The magnetometer switches the dynamic range between ± 8000 and± 60,000 nT, depending on the local magnetic field intensity. The experiment is calibrated by preflight tests and throughanalysis of in-orbit data. MGF data are edited into files witha common data file format, archived on a data server, andmade available to the science community. Magnetic fieldobservation by the MGF will significantly improve ourknowledge of the growth and decay of radiation belts andring currents, as well as the dynamics of geospace storms.

Keywords: EMIC wave, Geospace, Magnetic field,

Magnetometer, Radiation belts, Ring current,
ULF wave

Graphical abstract*Corresponding author: Ayako Matsuoka, matsuoka@isas.jaxa.jp

FULL PAPER

Open Access

Medium-energy particle experiments—electron analyzer (MEP-e) forthe exploration of energization and radiation in geospace (ERG)
mission
Satoshi Kasahara*, Shoichiro Yokota, Takefumi Mitani, Kazushi Asamura, Masafumi Hirahara,
Yasuko Shibano and Takeshi Takashima
Earth, Planets and Space 2018, 70:69 DOI:10.1186/s40623-018-0847-z
Received: 4 July 2017, Accepted: 19 April 2018, Published: 2 May 2018

Abstract
The medium-energy particle experiments—electron analyzer onboard the exploration of energization and radiation in
geospace spacecraft measures the energy and direction of each incoming electron in the energy range of 7–87 keV. The
sensor covers a 2π-radian disklike field of view with 16 detectors, and the full solid angle coverage is achieved through thespacecraft’s spin motion. The electron energy is independently measured by both an electrostatic analyzer and avalanche
photodiodes, enabling significant background reduction. We describe the technical approach, data output, and examples of
initial observations.

Keywords: Radiation belts, ERG

spacecraft, Medium-energy
particles

Graphical abstract*Corresponding author: Satoshi Kasahara, s.kasahara@eps.s.u‑tokyo.ac.jp
6Earth, Planets and Space

FULL PAPER

Open Access

Low-energy particle experiments–ion mass analyzer (LEPi)
onboard the ERG (Arase) satellite
K. Asamura*, Y. Kazama, S. Yokota, S. Kasahara and Y. Miyoshi
Earth, Planets and Space 2018, 70:70 DOI:10.1186/s40623-018-0846-0
Received: 14 September 2017, Accepted: 19 April 2018, Published: 2 May 2018

Abstract
Low-energy ion experiments–ion mass analyzer (LEPi) is one of the particle instruments onboard the ERG satellite. LEPi is an
ion energy-mass spectrometer which covers the range of particle energies from < 0.01 to 25 keV/q. Species of incoming ionsare discriminated by a combination of electrostatic energy-per-charge analysis and the time-of-flight technique. The sensor
has a planar field-of-view, which provides 4π steradian coverage by using the spin motion of the satellite. LEPi started its
nominal observation after the initial checkout and commissioning phase inspace.
a

Keywords: ERG satellite, Ion analyzer

Electrostac analyzer (ESA)TOF secon
MCP
Preamp
Digital electronics
High voltage power supply
CPU
Power supply

Graphical abstract

Fig. 3*Corresponding author: K. Asamura, asamura@stp.isas.jaxa.jp

FULL PAPER

Open Access

Design of a mission network system using SpaceWire forscientific payloads onboard the Arase spacecraft
Takeshi Takashima*, Emiko Ogawa, Kazushi Asamura and Mitsuru Hikishima
Earth, Planets and Space 2018, 70:71 DOI:10.1186/s40623-018-0839-z
Received: 7 September 2017, Accepted: 14 April 2018, Published: 4 May 2018

Abstract
Arase is a small scientific satellite program conducted by the Institute of Space and Astronautical Science/Japan Aerospace
Exploration Agency, which is dedicated to the detailed study of the radiation belts around Earth through in situ observations.
In particular, the goal is to directly observe the interaction between plasma waves and particles, which cause the generationof high-energy electrons. To observe the waves and particles in detail, we must record large volumes of burst data with hightransmission rates through onboard mission network systems.
For this purpose, we developed a high-speed and highly
reliable mission network based on SpaceWire, as well as a newand large memory data recorder equipped with a data searchfunction based on observation time (the time index, TI, is thesatellite time starting from when the spacecraft is poweredon.) with respect to the orbital data generated in large
quantities. By adopting a new transaction concept of a ring
topology network with SpaceWire, we could secure a
redundant mission network system without using large routersand having to suppress the increase in cable weight. We
confirmed that their orbit performs as designed.

Keywords: The ERG project, Radiation belts, Geospace,SpaceWire, Mission data processor

Graphical abstract*Corresponding author: Takeshi Takashima, ttakeshi@stp.isas.jaxa.jp
7

Ultra-thincarbon foil

Geospace Exploration by the ERG mission

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Open Access

Onboard software of Plasma Wave Experiment aboard Arase:
instrument management and signal processing of Waveform
Capture/Onboard Frequency Analyzer
Shoya Matsuda*, Yoshiya Kasahara, Hirotsugu Kojima, Yasumasa Kasaba, Satoshi Yagitani,
Mitsunori Ozaki, Tomohiko Imachi, Keigo Ishisaka, Atsushi Kumamoto, Fuminori Tsuchiya, Mamoru Ota,
Satoshi Kurita, Yoshizumi Miyoshi, Mitsuru Hikishima, Ayako Matsuoka and Iku Shinohara
Earth, Planets and Space 2018, 70:75 DOI:10.1186/s40623-018-0838-0
Received: 4 September 2017, Accepted: 14 April 2018, Published: 4 May 2018

Abstract
We developed the onboard processing software for the Plasma Wave Experiment (PWE) onboard the Exploration of energization and Radiation in Geospace, Arasesatellite. The PWE instrument has three receivers: Electric Field Detector, Waveform Capture/Onboard Frequency Analyzer (WFC/OFA), and the High-Frequency
Analyzer. We designed a pseudo-parallel processing scheme with a time-sharing system and achieved simultaneous signal processing for each receiver. Since electricand magnetic field signals are processed by the different CPUs, we developed a synchronized observation system by using shared packets on the mission network.
The OFA continuously measures the power spectra, spectral matrices, and complex spectra. The OFA obtains not only the entire ELF/VLF plasma waves’ activity but
also the detailed properties (e.g., propagation direction and polarization) of the observed plasma waves. We performed simultaneous observation of electric andmagnetic field data and successfully obtained clear wave properties of whistler-mode chorus waves using these data. In order to measure raw waveforms, wedeveloped two modes for the WFC, ‘chorus burst mode’ (65,536 samples/s) and ‘EMIC burst mode’ (1024 samples/s), for the purpose of the measurement of thewhistler-mode chorus waves (typically in a frequency range from several hundred Hz to several kHz) andthe EMIC waves (typically in a frequency range from a few Hz to several hundred Hz), respectively. We
successfully obtained the waveforms of electric and magnetic fields of whistler-mode chorus waves andion cyclotron mode waves along the Arase’s orbit. We also designed the software-type wave–particle
interaction analyzer mode. In this mode, we measure electric and magnetic field waveforms
continuously and transfer them to the mission data recorder onboard the Arase satellite. We also
installed an onboard signal calibration function (onboard SoftWare CALibration; SWCAL). We performed
onboard electric circuit diagnostics and antenna impedance measurement of the wire-probe antennas
along the orbit. We utilize the results obtained using the SWCAL function when we calibrate the spectra
and waveforms obtained by the PWE.

Keywords: Arase satellite, ERG, PWE, Plasma wave, Geospace, Radiation belt, Onboard

Fig. 7processing, Chorus wave, EMIC wave, Magnetosonic wave

*Corresponding author: Shoya Matsuda, matsuda@isee.nagoya‑u.ac.jp

FULL PAPER

Open Access

Magnetic Search Coil (MSC) of Plasma Wave Experiment (PWE) aboard
the Arase (ERG) satellite
Mitsunori Ozaki*, Satoshi Yagitani, Yoshiya Kasahara, Hirotsugu Kojima, Yasumasa Kasaba,
Atsushi Kumamoto, Fuminori Tsuchiya, Shoya Matsuda, Ayako Matsuoka, Takashi Sasaki
and Takahiro Yumoto
Earth, Planets and Space 2018, 70:76 DOI:10.1186/s40623-018-0837-1
Received: 22 August 2017, Accepted: 14 April 2018, Published: 4 May 2018

Abstract
This paper presents detailed performance values of the Magnetic Search Coil (MSC) that is part of the Plasma Wave
Experiment on board the Arase (ERG) satellite. The MSC consists of a three-axis search coil magnetometer with a 200-mm-longmagnetic core. The MSC plays a central role in the magnetic field observations, particularly for whistler mode chorus and hisswaves in a few kHz frequency range, which may cause local acceleration and/or rapid loss of radiation belt electrons.
Accordingly, the MSC was carefully designed and developed to operate well in harsh radiation environments. To ascertain the
wave-normal vectors, polarizations, and refractive indices of the plasma waves in a wide frequency band, the output signals
detected by the MSC are fed into the two different wave receivers: one is the WaveForm Capture/Onboard Frequency Analyzer
for waveform and spectrum observations in the frequency range from a few Hz up to 20 kHz, and the other is the HighFrequency Analyzer for spectrum observations in the frequency range from 10 to 100 kHz. The noise equivalent magnetic
induction of the MSC is 20 fT/Hz1/2 at a frequency of 2 kHz,and the null depth of directionality is − 40 dB, which is10
equivalent to an angular error less than 1°. The MSC on
1010board the Arase satellite is the first experiment using a10
current-sensitive preamplifier for probing the plasma
1010
waves in the radiation belts.
7

NEMI (fT/Hz

1/2

)

6

Magnetosonic waves

4

Chorus and hiss waves

3
2

Van Allen Probes

101

Keywords: Search coil magnetometer, Arase (ERG)

100
10-1

satellite, Plasma waves, Radiation belts,
Geospace

Large
whistler

EMIC waves

5

100

101

102

103

Frequency (Hz)Graphical abstract*Corresponding author: Mitsunori Ozaki, ozaki@is.t.kanazawa‑u.ac.jp
8

104

105

Earth, Planets and Space

FULL PAPER

Open Access

High-energy electron experiments (HEP) aboard the ERG(Arase) satellite
Takefumi Mitani*, Takeshi Takashima, Satoshi Kasahara, Wataru Miyake and Masafumi Hirahara
Earth, Planets and Space 2018, 70:77 DOI:10.1186/s40623-018-0853-1
Received: 4 October 2017, Accepted: 25 April 2018, Published: 8 May 2018

Abstract
This paper reports the design, calibration, and operation of high-energy electron experiments (HEP) aboard the exploration ofenergization and radiation in geospace (ERG) satellite. HEP detects 70 keV–2 MeV electrons and generates a threedimensional velocity distribution for these electrons in every period of the satellite’s rotation. Electrons are detected by two
instruments, namely HEP-L and HEP-H, which differ in their geometric factor (G-factor) and range of energies they detect.
HEP-L detects 70 keV–1 MeV electrons and its G-factor is 9.3 × 10−4 cm2 sr at maximum, while HEP-H observes 0.7–2 MeV
electrons and its G-factor is 9.3 × 10−3 cm2 sr at maximum. The instruments utilize silicon strip detectors and applicationspecific integrated circuits to readout the incident charge signal from each
strip. Before the launch, we calibrated the detectors by measuring the energy
spectra of all strips using γ-ray sources. To evaluate the overall performance ofthe HEP instruments, we measured the energy spectra and angular responses
with electron beams. After HEP was first put into operation, on February 2,
2017, it was demonstrated that the instruments performed normally. HEP
began its exploratory observations with regard to energization and radiationin geospace in late March 2017. The initial results of the in-orbit observations
are introduced briefly in this paper.

Keywords: ERG, Arase, Radiation belts, High-energy electrons
Graphical abstract*Corresponding author: Takefumi Mitani, mitani@planeta.sci.isas.jaxa.jp

FULL PAPER

Open Access

Data processing in Software-type Wave–Particle Interaction Analyzer
onboard the Arase satellite
Mitsuru Hikishima*, Hirotsugu Kojima, Yuto Katoh, Yoshiya Kasahara, Satoshi Kasahara,
Takefumi Mitani, Nana Higashio, Ayako Matsuoka, Yoshizumi Miyoshi, Kazushi Asamura,Takeshi Takashima, Shoichiro Yokota, Masahiro Kitahara and Shoya Matsuda
Earth, Planets and Space 2018, 70:80 DOI:10.1186/s40623-018-0856-y
Received: 7 September 2017, Accepted: 1 May 2018, Published: 11 May 2018

Abstract
The software-type wave–particle interaction analyzer (S-WPIA) is an instrument package onboard the Arase satellite, which
studies the magnetosphere. The S-WPIA represents a new method for directly observing wave–particle interactions onboard a
spacecraft in a space plasma environment. The main objective of the S-WPIA is to quantitatively detect wave–particle
interactions associated with whistler-mode chorus emissions and electrons over a wide energy range (from several keV toseveral MeV). The quantity of energy exchanges between waves and particles can be represented as the inner product of the
wave electric-field vector and the particle velocity vector. The S-WPIA requires accurate measurement of the phase difference
between wave and particle gyration. The leading edge of the S-WPIA system allows us to collect comprehensive information,
including the detection time, energy, and incoming direction of individual particles and instantaneous-wave electric andmagnetic fields, at a high sampling rate. All the collected particle and waveform data are stored in the onboard large-volumedata storage. The S-WPIA executes calculations asynchronously using theWAVE E1, E2, B1, B2, B3
collected electric and magnetic wave data, data acquired from multiple particle
PARTICLE
Calibration
FFT
IFFT
instruments, and ambient magnetic-field data. The S-WPIA has the role ofhandling large amounts of raw data that are dedicated to calculations of theCoordinate conversion
S-WPIA. Then, the results are transferred to the ground station. This paper
External magnetic field
describes the design of the S-WPIA and its calculations in detail, as implemented
onboard Arase.

Keywords: Wave–particle interaction, Onboard processing, Inner
magnetosphere

Graphical abstract*Corresponding author: Mitsuru Hikishima, hikishima@stp.isas.jaxa.jp
9Geospace Exploration by the ERG mission

FULL PAPER

Open AccessHigh Frequency Analyzer (HFA) of Plasma Wave Experiment (PWE)
onboard the Arase spacecraft
Atsushi Kumamoto*, Fuminori Tsuchiya, Yoshiya Kasahara, Yasumasa Kasaba, Hirotsugu Kojima,
Satoshi Yagitani, Keigo Ishisaka, Tomohiko Imachi, Mitsunori Ozaki, Shoya Matsuda,
Masafumi Shoji, Aayako Matsuoka, Yuto Katoh, Yoshizumi Miyoshi and Takahiro Obara
Earth, Planets and Space 2018, 70:82 DOI:10.1186/s40623-018-0854-0
Received: 6 September 2017, Accepted: 25 April 2018, Published: 16 May 2018

Abstract
The High Frequency Analyzer (HFA) is a subsystem of the Plasma Wave Experiment onboard the Arase (ERG) spacecraft. The main purposes of the HFA include (1) determining theelectron number density around the spacecraft from observations of upper hybrid resonance (UHR) waves, (2) measuring the electromagnetic field component of whistler-mode
chorus in a frequency range above 20 kHz, and (3) observing radio and plasma waves excited in the storm-time magnetosphere. Two components of AC electric fields detectedby Wire Probe Antenna and one component of AC magnetic fields detected by Magnetic Search Coils are fed to theaHFA. By applying analog and digital signal processing in the HFA, the spectrograms of two electric fields (EE mode) or
one electric field and one magnetic field (EB mode) in a frequency range from 10 kHz to 10 MHz are obtained at aninterval of 8 s. For the observation of plasmapause, the HFA can also be operated in PP (plasmapause) mode, in which
spectrograms of one electric field component below 1 MHz are obtained at an interval of 1 s. In the initial HFA
operations from January to July, 2017, the following results are obtained: (1) UHR waves, auroral kilometric radiation(AKR), whistler-mode chorus, electrostatic electron cyclotron harmonic waves, and nonthermal terrestrial continuum
radiation were observed by the HFA in geomagnetically quiet and disturbed conditions. (2) In the test operations of
the polarization observations on June 10, 2017, the fundamental R-X and L-O mode AKR and the second-harmonic R-X
mode AKR from different sources in the northern polar region were observed. (3) The semiautomatic UHR frequencybidentification by the computer and a human operator was applied to the HFA spectrograms. In the identification by
the computer, we used an algorithm for narrowing down the candidates of UHR frequency by checking intensity andbandwidth. Then, the identified UHR frequency by the computer was checked and corrected if needed by the humanoperator. Electron number density derived from the determined UHR frequency will be useful for the investigation of
the storm-time evolution of the plasmasphere and topside ionosphere.
10 2017-03-26

10

-5

10

-8

Spectral intensity [V m-1Hz-1/2 ]Frequency [MHz]

a

AKR

1

0.1

UHR

Whistler

0.01
UT
00:00
R
5.457
MLAT -2.5
MLT
5.1
L
5.412
10

06:00
5.495
-4.9
3.0
5.621

12:00
1.805
34.1
10.3
2.628

15:00
5.126
-19.3
2.9
5.697

18:00
5.932
-6.3
4.5
5.924

21:00
2.828
17.6
7.5
3.046

00:00
4.650
-21.7
2.1
5.406

2017-03-27

10

-5

10

-8

AKR

1

UHR

NTC

0.1

ESCH

Keywords: The Arase (ERG) spacecraft, Plasma Wave Experiment (PWE), High Frequency Analyzer (HFA), Upper

hybrid resonance (UHR) wave, Auroral kilometric radiation (AKR), Whistler-mode chorus, Electrostatic
electron cyclotron harmonic (ESCH) wave, Nonthermal terrestrial continuum (NTC) radiation,
Electron number density, Plasmasphere

09:00
5.740
12.2
4.8
6.080

Spectral intensity [V m-1Hz-1/2 ]Frequency [MHz]

b

03:00
1.074
0.0
16.5
1.049

Whistler
0.01
UT
00:00
R
4.650
MLAT -21.7
MLT
2.1
L
5.406

03:00
6.038
-3.4
4.2
6.096

06:00
3.668
17.2
6.8
4.054

09:00
4.050
-13.2
1.8
4.301

12:00
6.061
2.7
3.9
6.088

15:00
4.344
17.8
5.7
4.780

18:00
3.303
-35.0
0.8
4.917

21:00
6.000
-15.3
3.7
6.376

00:00
4.884
2.0
5.5
4.827

Fig. 2*Corresponding author: Atsushi Kumamoto, kumamoto@stpp.gp.tohoku.ac.jp

FULL PAPER

Open Access

The Plasma Wave Experiment (PWE) on board the Arase (ERG) satellite
Yoshiya Kasahara*, Yasumasa Kasaba, Hirotsugu Kojima, Satoshi Yagitani, Keigo Ishisaka,
Atsushi Kumamoto, Fuminori Tsuchiya, Mitsunori Ozaki, Shoya Matsuda, Tomohiko Imachi,
Yoshizumi Miyoshi, Mitsuru Hikishima, Yuto Katoh, Mamoru Ota, Masafumi Shoji, Ayako Matsuoka
and Iku Shinohara
Earth, Planets and Space 2018, 70:86 DOI:10.1186/s40623-018-0842-4
Received: 6 September 2017, Accepted: 14 April 2018, Published: 21 May 2018

Abstract
The Exploration of energization and Radiation in Geospace (ERG) project aims to study acceleration and loss mechanisms of relativistic electrons
around the Earth. The Arase (ERG) satellite was launched on December 20, 2016, to explore in the heart of the Earth’s radiation belt. In the present
paper, we introduce the specifications of the Plasma Wave Experiment (PWE) on board the Arase satellite. In the inner magnetosphere, plasma waves,such as the whistler-mode chorus, electromagnetic ion cyclotron wave, and magnetosonic wave, are expected to interact with particles over a wide
energy range and contribute to high-energy particle loss and/or acceleration processes. Thermal plasma density is another key parameter because it
controls the dispersion relation of plasma waves, which affects wave–particle interaction conditions and wave propagation characteristics. The DC
electric field also plays an important role in controlling the global dynamics of the inner magnetosphere. The PWE, which consists of an orthogonalelectric field sensor (WPT; wire probe antenna), a triaxial magnetic sensor (MSC; magnetic search coil), and receivers named electric field detector(EFD), waveform capture and onboard frequency analyzer (WFC/OFA), and high-frequency analyzer (HFA), was developed to measure the DC electricfield and plasma waves in the inner magnetosphere. Using these sensors andreceivers, the PWE covers a wide frequency range from DC to 10 MHz for electricfields and from a few Hz to 100 kHz for magnetic fields. We produce continuous ELF/
VLF/HF range wave spectra and ELF range waveforms for 24 h each day. We also
produce spectral matrices as continuous data for wave direction finding. In addition,
we intermittently produce two types of waveform burst data, “chorus burst” and“EMIC burst.” We also input raw waveform data into the software-type wave–particle
interaction analyzer (S-WPIA), which derives direct correlation between waves andparticles. Finally, we introduce our PWE observation strategy and provide some initial
results.

Keywords: Plasma wave, Radiation belt, Geospace, Inner magnetosphere, Chorus*Corresponding author: Yoshiya Kasahara, kasahara@is.t.kanazawa‑u.ac.jp
10Fig. 20

Earth, Planets and Space

FULL PAPER

Open AccessGeospace exploration project ERG
Yoshizumi Miyoshi*, Iku Shinohara, Takeshi Takashima, Kazushi Asamura, Nana Higashio,
Takefumi Mitani, Satoshi Kasahara, Shoichiro Yokota, Yoichi Kazama, Shiang-Yu Wang,
Sunny W. Y. Tam, Paul T. P. Ho, Yoshiya Kasahara, Yasumasa Kasaba, Satoshi Yagitani,
Ayako Matsuoka, Hirotsugu Kojima, Yuto Katoh, Kazuo Shiokawa and Kanako Seki

10

[kHz]

10-1

PWE/EFD

[keV]

HEP

[keV]

e

XEP

MEP-e

h

LEP-e

i

MEP-i
(H+)

j

LEP-i
(H+)

k

PWE/EFD(potential)

l

MGF

m AL

[keV/q]

[keV]

[keV]

g

10-2
1
10-2
10-4
10-6

10-2
5x103

103
102
10
1

103
103
5x102

104
103
102
10
1
107
106
105
104
103
105
104
103
102
10
1

102
102
5x10
10
10
1
10-1
10-2
102
5x10

105
104
103

10
10
1
10-1
10-2
5
-5
-15
-25
104
103
102
0
-400
-800

MLT
MLAT
Lm
hhmm
2017

102
1

1
10-1

103
102
10
1
10-1

1.0
-19.5
4.7
0000
Apr 09

3.9
6.8
6.0
0400

19.0
-32.5
1.8
0800

2.9
2.4
6.0
1200

5.8
24.3
4.2
1600

2.2
-18.7
5.8
2000

[mV2/m 2/Hz][pT2/Hz]

PWE/OFA(B)

[kHz]

c
d
e

-90

-1

[mV2/m 2/Hz]

10-1
10-3
10-5
10-7

10

-70

[cnt/sec]

[kHz]

1

[cnt/sec] [/cm2/s/sr/keV] [cnt/sample]

PWE/OFA(E)10[cnt/sample] [/cm2/s/sr/keV]

-50

[kHz]

104
103
102
10

[keV/q]Geospaceb

PWE/HFA[V]

Keywords: The ERG project, The ERG (Arase) satellite, The radiation belts,

a

[nT]

The Exploration of energization and Radiation in Geospace (ERG) project explores
the acceleration, transport, and loss of relativistic electrons in the radiation belts
and the dynamics for geospace storms. This project consists of three researchteams for satellite observation, ground-based network observation, and integrated
data analysis/simulation. This synergetic approach is essential for obtaining acomprehensive understanding of the relativistic electron generation/loss processesof the radiation belts as well as geospace storms through cross-energy/crossregional couplings, in which different plasma/particle populations and regions arestrongly coupled with each other. This paper gives an overview of the ERG projectand presents the initial results from the ERG (Arase) satellite.

[nT]

Abstract[dBVpp]Earth, Planets and Space 2018, 70:101 DOI:10.1186/s40623-018-0862-0
Received: 16 April 2018, Accepted: 15 May 2018, Published: 26 June 2018

4.6
4.3
5.3
0000
Apr 10Fig. 6*Corresponding author: Yoshizumi Miyoshi, miyoshi@isee.nagoya‑u.ac.jp

FULL PAPER

Open Access

Exploration of energization and radiation in geospace (ERG): challenges,
development, and operation of satellite systems
Yosuke Nakamura*, Seisuke Fukuda, Yasuko Shibano, Hiroyuki Ogawa, Shin-ichiro Sakai,
Shigehito Shimizu, Ersin Soken, Yu Miyazawa, Hiroyuki Toyota, Akio Kukita, Yusuke Maru,
Junichi Nakatsuka, Tomohiko Sakai, Shinsuke Takeuchi, Kenichiro Maki, Makoto Mita, Emiko Ogawa,Yuya Kakehashi, Kumi Nitta, Kazushi Asamura, Takeshi Takashima and Iku Shinohara
Earth, Planets and Space 2018, 70:102 DOI:10.1186/s40623-018-0863-z
Received: 10 October 2017, Accepted: 16 May 2018, Published: 26 June 2018

Abstract
The exploration of energization and radiation in geospace (ERG) satellite, nicknamed “Arase,” is the second satellite in a series of small scientificsatellites created by the Institute of Space and Astronautical Science of the Japan Aerospace Exploration Agency. It was launched on
December 20, 2016, by the Epsilon launch vehicle. The purpose of the ERG project is to investigate how high-energy (over MeV) electrons in
the radiation belts surrounding Earth are generated and lost by monitoring the interactions between plasma waves and electrically charged
particles. To measure these physical processes in situ, the ERG satellite traverses the heart of the radiation belts. The orbit of the ERG is highly
elliptical and varies due to the perturbation force: the apogee altitude is approximately 32,200–32,300 km, and the perigee altitude is 340–
440 km. In this study, we introduce the scientific background for this project and four major challenges that need to be addressed toeffectively carry out this scientific mission with a small satellite: (1) dealing with
Index pulse generation
Transmitter OFF mode change
Index pulse generation
harsh environmental conditions in orbit and electromagnetic compatibility
Higher-rate comm. mode.
mode changee.g. 0.5 Mbps or 1Mbps
issues, (2) spin attitude stabilization and avoiding excitation of the libration by
Shadow
flexible structures, (3) attaining an appropriate balance between the mission
Ground station
requirements and the limited resources of the small satellite, and (4) the
MTQ drive at altitude
Operation pass
lower than 4000km
adaptation and use of a flexible standardized bus. In this context, we describe
for sun pointing
the development process and the flight operations for the satellite, which is
ERG
MTQ
Lower-late comm. mode.
currently working as designed and obtaining excellent data in its mission.
demagnetization
Ranging withe.g. 4 kbps or 64 kbps
lower late comm. mode

Keywords: ERG, Arase, Radiation belts, Van Allen belts, Geospace, Smallsatellite, ProjectTransmitter ON

Higher-rate comm. mode.
e.g. 0.5 Mbps or 1Mbps

Fig. 17*Corresponding author: Yosuke Nakamura, nakamura.yosuke@jaxa.jp
11

Antenna select changeGeospace Exploration by the ERG mission

FULL PAPER

Open Access

The extremely high-energy electron experiment (XEP)
onboard the Arase (ERG) satellite
Nana Higashio*, Takeshi Takashima, Iku Shinohara and Haruhisa Matsumoto
Earth, Planets and Space 2018, 70:134 DOI:10.1186/s40623-018-0901-x
Received: 20 May 2018, Accepted: 1 August 2018, Published: 16 August 2018

Abstract
The extremely high-energy electron experiment (XEP) onboard the Arase (ERG) satellite is designed to measure high-energy
electrons in the Earth’s radiation belts. The XEP was developed by taking advantage of our technical heritage of high-energy
particle detectors that are onboard Earth observation satellites of the Japan Aerospace Exploration Agency (JAXA) as theradiation monitor. The main target of the XEP is to precisely measure variations of relativistic electrons in the outer radiation
belt even during magnetic storms. The measurement is scientifically required to address physical mechanisms of electron
acceleration and loss. The XEP consists of five solid-state silicon detectors (SSDs) and a single-crystal inorganic scintillator of
cerium-doped gadolinium orthosilicate (GSO) to measure electrons in the energy range of 0.4–20 MeV and has a 20° single
field of view (FOV). It is also equipped with a plastic scintillator that surrounds the GSO scintillator to prevent particles fromentering the detectors from outside the FOV. The
10ab
XEP has started its observation of relativisticcollimator
electrons and has successfully observed dynamic
Detection Unit
HV circuit board
Detection Unitvariations of relativistic electron fluxes in the outer
MLI Thermal
blankets
Base plateradiation belt during magnetic storms. This paper
HV section
describes the instrumentation of the XEP and
Analog circuit board
Base plate
presents an example of initial observation results.
Digital circuit board
Circuit section

CPU

Keywords: ERG, Radiation belts, Extremely

PSU

high-energy electron experimentFig. 1*Corresponding author: Nana Higashio, higashio.nana@jaxa.jp

TECHNICAL REPORT

Open Access

Visualization tool for three-dimensional plasma velocity distributions(ISEE_3D) as a plug-in for SPEDAS
Kunihiro Keika*, Yoshizumi Miyoshi, Shinobu Machida, Akimasa Ieda, Kanako Seki, Tomoaki Hori,
Yukinaga Miyashita, Masafumi Shoji, Iku Shinohara, Vassilis Angelopoulos, Jim W. Lewis and Aaron Flores
Earth, Planets and Space 2017, 69:170 DOI:10.1186/s40623-017-0761-9
Received: 28 March 2017, Accepted: 10 December 2017, Published: 21 December 2017

Abstract
This paper introduces ISEE_3D, an interactive visualization tool for three-dimensional plasma velocity distribution functions, developedby the Institute for Space-Earth Environmental Research, Nagoya University, Japan. The tool provides a variety of methods to visualize
the distribution function of space plasma: scatter, volume, and isosurface modes. The tool also has a wide range of functions, such as
displaying magnetic field vectors and two-dimensional slices of distributions to facilitate extensive analysis. The coordinatetransformation to the magnetic field coordinates is also implemented in the tool. The source codes of the tool are written as scripts of awidely used data analysis software language, Interactive Data Language, which has been widespread in the field of space physics andsolar physics. The current version of the tool can be used for data files of the plasma distribution function from the Geotail satellite
mission, which are publicly accessible through the Data Archives and Transmission
System of the Institute of Space and Astronautical Science (ISAS)/Japan Aerospace
Exploration Agency (JAXA). The tool is also available in the Space Physics
Environment Data Analysis Software to visualize plasma data from theMagnetospheric Multiscale and the Time History of Events and MacroscaleInteractions during Substorms missions. The tool is planned to be applied to datafrom other missions, such as Arase (ERG) and Van Allen Probes after replacing or
adding data loading plug-ins. This visualization tool helps scientists understand the
dynamics of space plasma better, particularly in the regions where themagnetohydrodynamic approximation is not valid, for example, the Earth’s innermagnetosphere, magnetopause, bow shock, and plasma sheet.

Keywords: Velocity distributions of space plasma, In situ measurements ofspace plasma, Interactive visualization tool, The ERG project*Corresponding author: Kunihiro Keika, keika@eps.s.u‑tokyo.ac.jp
12Fig. 5

Earth, Planets and SpaceTECHNICAL REPORT

Open Access

The ERG Science Center
Yoshizumi Miyoshi*, Tomoaki Hori, Masafumi Shoji, Mariko Teramoto, T. F. Chang, Tomonori Segawa,
Norio Umemura, Shoya Matsuda, Satoshi Kurita, Kunihiro Keika, Yukinaga Miyashita, Kanako Seki,
Yoshimasa Tanaka, Nozomu Nishitani, Satoshi Kasahara, Shoichiro Yokota, Ayako Matsuoka,
Yoshiya Kasahara, Kazushi Asamura, Takeshi Takashima and Iku Shinohara
Earth, Planets and Space 2018, 70:96 DOI:10.1186/s40623-018-0867-8
Received: 4 September 2017, Accepted: 23 May 2018, Published: 15 June 2018

Abstract
The Exploration of energization andRadiation in Geospace (ERG) Science
Center serves as a hub of the ERG project,providing data files in a common format
and developing the space physics
environment data analysis software andplug-ins for data analysis. The Science
Center also develops observation plans
for the ERG (Arase) satellite according to
the science strategy of the project.
Conjugate observations with othersatellites and ground-based observations
are also planned. These tasks contribute to
the ERG project by achieving quick
analysis and well-organized conjugate
ERG satellite and ground-based
observations.
Graphical abstract

Corresponding author: Yoshizumi Miyoshi, miyoshi@isee.nagoya‑u.ac.jp

OBITUARYOpen AccessIn memory of Professor Takayuki Ono
Earth, Planets and Space 2018, 70:172
DOI:10.1186/s40623-018-0939-9
Published: 31 October 2018

Professor Takayuki Ono of Graduate School of Science, Tohoku University, passed away on 21
December 2013. He was 63 years old. He was the Principal Investigator of the Geospace
Exploration Mission: Exploration in energization and Radiation in Geospace (ERG) and played
the leader of the ERG project. It is very unfortunate that he did not live long enough towitness the launch of the ERG (Arase) satellite on 20 December 2016 to which he had
dedicated to so much of his life. His warm character appeared to everyone, and he had always
encouraged young colleagues to realize the project.
Professor Ono was born on 5 August 1950. He graduated and received a Ph.D. from Tohoku
University. He moved to National Institute of Polar Research in 1980. He came back to Tohoku
University to take up the position of an associate professor and was promoted to a full
professor in 2000. He is survived by his wife Naomi, four children, and five grandchildren.
Y. Miyoshi, T. Takashima, K. Asamura and I. Shinohara

13

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Geospace exploration project ERG. . . . . . . . . . . . . . . . . . . . . . . . . . . . Yoshizumi Miyoshi, Iku Shinohara, Takeshi Takashima, Kazushi Asamura, Nana Higashio, Takefumi Mitani,

Satoshi Kasahara, Shoichiro Yokota, Yoichi Kazama, Shiang-Yu Wang, Sunny W. Y. Tam, Paul T. P. Ho,
Yoshiya Kasahara, Yasumasa Kasaba, Satoshi Yagitani, Ayako Matsuoka, Hirotsugu Kojima,
Yuto Katoh, Kazuo Shiokawa and Kanako Seki   11Exploration of energization and radiation in geospace (ERG): challenges, development, and operation of satellite systems. . . . . . . . . . . . . . . . . . . . . . . . . . Yosuke Nakamura, Seisuke Fukuda, Yasuko Shibano, Hiroyuki Ogawa, Shin-ichiro Sakai, Shigehito Shimizu,

Ersin Soken, Yu Miyazawa,Hiroyuki Toyota, Akio Kukita, Yusuke Maru, Junichi Nakatsuka, Tomohiko Sakai,
Shinsuke Takeuchi, Kenichiro Maki, Makoto Mita, Emiko Ogawa, Yuya Kakehashi, Kumi Nitta,
Kazushi Asamura, Takeshi Takashima and Iku Shinohara   11The extremely high-energy electron experiment (XEP) onboard the Arase (ERG) satellite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nana Higashio, Takeshi Takashima, Iku Shinohara and Haruhisa Matsumoto   12Visualization tool for three-dimensional plasma velocity distributions (ISEE_3D) as a plug-in for SPEDAS. . . . . . . . . . . . . . . Kunihiro Keika, Yoshizumi Miyoshi, Shinobu Machida, Akimasa Ieda, Kanako Seki, Tomoaki Hori, Yukinaga Miyashita,
Masafumi Shoji, Iku Shinohara, Vassilis Angelopoulos, Jim W. Lewis and Aaron Flores   12The ERG Science Center. . . . . . . . . . . . . . . Yoshizumi Miyoshi, Tomoaki Hori, Masafumi Shoji, Mariko Teramoto, T. F. Chang, Tomonori Segawa, Norio Umemura,

Shoya Matsuda, Satoshi Kurita, Kunihiro Keika, Yukinaga Miyashita, Kanako Seki, Yoshimasa Tanaka,
Nozomu Nishitani, Satoshi Kasahara, Shoichiro Yokota, Ayako Matsuoka, Yoshiya Kasahara,
Kazushi Asamura, Takeshi Takashima and Iku Shinohara   13In memory of Professor Takayuki Ono. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   13Contents
Special issue “Geospace Exploration by the ERG mission”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tsugunobu Nagai, Barry Mauk, Ondrej Santolik, Takashi Kubota and Takeshi Sakanoi
Ground-based instruments of the PWING project to investigate dynamics of the inner magnetosphere at subauroral
latitudes as a part of the ERG-ground coordinated observation network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kazuo Shiokawa, Yasuo Katoh, Yoshiyuki Hamaguchi, Yuka Yamamoto, Takumi Adachi, Mitsunori Ozaki,
Shin-Ichiro Oyama, Masahito Nosé, Tsutomu Nagatsuma, Yoshimasa Tanaka, Yuichi Otsuka, Yoshizumi Miyoshi,
Ryuho Kataoka, Yuki Takagi, Yuhei Takeshita, Atsuki Shinbori, Satoshi Kurita, Tomoaki Hori, Nozomu Nishitani,Iku Shinohara, Fuminori Tsuchiya, Yuki Obana, Shin Suzuki, Naoko Takahashi, Kanako Seki, Akira Kadokura,
Keisuke Hosokawa, Yasunobu Ogawa, Martin Connors, J. Michael Ruohoniemi, Mark Engebretson, Esa Turunen,
Thomas Ulich, Jyrki Manninen, Tero Raita, Antti Kero, Arto Oksanen, Marko Back, Kirsti Kauristie,
Jyrki Mattanen, Dmitry Baishev, Vladimir Kurkin, Alexey Oinats, Alexander Pashinin,
Roman Vasilyev, Ravil Rakhmatulin, William Bristow and Marty Karjala

Low-energy particle experiments–electron analyzer (LEPe) onboard the Arase spacecraft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yoichi Kazama, Bo-Jhou Wang, Shiang-Yu Wang, Paul T. P. Ho, Sunny W. Y. Tam, Tzu-Fang Chang,
Chih-Yu Chiang and Kazushi Asamura

Medium-energy particle experiments–ion mass analyzer (MEP-i) onboard ERG (Arase). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shoichiro Yokota, Satoshi Kasahara, Takefumi Mitani, Kazushi Asamura, Masafumi Hirahara,
Takeshi Takashima, Kazuhiro Yamamoto and Yasuko Shibano

1

3
3
4

Wire Probe Antenna (WPT) and Electric Field Detector (EFD) of Plasma Wave Experiment (PWE) aboard the Arase satellite:
specifications and initial evaluation results. . . . . . . . . . . . . . . . . . . . . . . . . . . Yasumasa Kasaba, Keigo Ishisaka, Yoshiya Kasahara, Tomohiko Imachi, Satoshi Yagitani, Hirotsugu Kojima,

Shoya Matsuda, Masafumi Shoji, Satoshi Kurita, Tomoaki Hori, Atsuki Shinbori, Mariko Teramoto,
Yoshizumi Miyoshi, Tomoko Nakagawa, Naoko Takahashi, Yukitoshi Nishimura, Ayako Matsuoka,
Atsushi Kumamoto, Fuminori Tsuchiya and Reiko Nomura

4

Software-type Wave–Particle Interaction Analyzer on board the Arase satellite. . . . . . . . . . . . . . . . . . . . . . . . . Yuto Katoh, Hirotsugu Kojima, Mitsuru Hikishima, Takeshi Takashima, Kazushi Asamura, Yoshizumi Miyoshi,
Yoshiya Kasahara, Satoshi Kasahara, Takefumi Mitani, Nana Higashio, Ayako Matsuoka, Mitsunori Ozaki,
Satoshi Yagitani, Shoichiro Yokota, Shoya Matsuda, Masahiro Kitahara and Iku Shinohara

5

Theory, modeling, and integrated studies in the Arase (ERG) project. . . . . . . . . . . . . . . . . . . . . . . . Kanako Seki, Yoshizumi Miyoshi, Yusuke Ebihara, Yuto Katoh, Takanobu Amano, Shinji Saito, Masafumi Shoji,
Aoi Nakamizo, Kunihiro Keika, Tomoaki Hori, Shin’ya Nakano, Shigeto Watanabe, Kei Kamiya, Naoko Takahashi,
Yoshiharu Omura, Masahito Nosé, Mei-Ching Fok, Takashi Tanaka, Akimasa Ieda and Akimasa Yoshikawa

5

The ARASE (ERG) magnetic field investigation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ayako Matsuoka, Mariko Teramoto, Reiko Nomura, Masahito Nosé, Akiko Fujimoto, Yoshimasa Tanaka,

Manabu Shinohara, Tsutomu Nagatsuma, Kazuo Shiokawa, Yuki Obana, Yoshizumi Miyoshi,
Makoto Mita, Takeshi Takashima and Iku Shinohara

Medium-energy particle experiments—electron analyzer (MEP-e) for the exploration of energization and radiation in
geospace (ERG) mission . . . . . . . . . . . . . Satoshi Kasahara, Shoichiro Yokota, Takefumi Mitani, Kazushi Asamura, Masafumi Hirahara,
Yasuko Shibano and Takeshi Takashima

Low-energy particle experiments–ion mass analyzer (LEPi) onboard the ERG (Arase) satellite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K. Asamura, Y. Kazama, S. Yokota, S. Kasahara and Y. Miyoshi
Design of a mission network system using SpaceWire for scientific payloads onboard the Arase spacecraft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Takeshi Takashima, Emiko Ogawa, Kazushi Asamura and Mitsuru Hikishima
Onboard software of Plasma Wave Experiment aboard Arase: instrument management and signal processing of
Waveform Capture/Onboard Frequency Analyzer. . . . . . . . . . . . . . . . . . . . . . . . . . . Shoya Matsuda, Yoshiya Kasahara, Hirotsugu Kojima, Yasumasa Kasaba, Satoshi Yagitani, Mitsunori Ozaki,

Tomohiko Imachi, Keigo Ishisaka, Atsushi Kumamoto, Fuminori Tsuchiya, Mamoru Ota, Satoshi Kurita,
Yoshizumi Miyoshi, Mitsuru Hikishima, Ayako Matsuoka and Iku Shinohara

Magnetic Search Coil (MSC) of Plasma Wave Experiment (PWE) aboard the Arase (ERG) satellite. . . . . . . . . . . . . . . . . . . . . . . Mitsunori Ozaki, Satoshi Yagitani, Yoshiya Kasahara, Hirotsugu Kojima, Yasumasa Kasaba, Atsushi Kumamoto,
Fuminori Tsuchiya, Shoya Matsuda, Ayako Matsuoka, Takashi Sasaki and Takahiro Yumoto

High-energy electron experiments (HEP) aboard the ERG (Arase) satellite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Takefumi Mitani, Takeshi Takashima, Satoshi Kasahara, Wataru Miyake and Masafumi Hirahara
Data processing in Software-type Wave–Particle Interaction Analyzer onboard the Arase satellite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mitsuru Hikishima, Hirotsugu Kojima, Yuto Katoh, Yoshiya Kasahara, Satoshi Kasahara, Takefumi Mitani,
Nana Higashio, Ayako Matsuoka, Yoshizumi Miyoshi, Kazushi Asamura, Takeshi Takashima,
Shoichiro Yokota, Masahiro Kitahara and Shoya Matsuda

6

6
7
7

8
8
9

9

High Frequency Analyzer (HFA) of Plasma Wave Experiment (PWE) onboard the Arase spacecraft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Atsushi Kumamoto, Fuminori Tsuchiya, Yoshiya Kasahara, Yasumasa Kasaba, Hirotsugu Kojima,
Satoshi Yagitani, Keigo Ishisaka, Tomohiko Imachi, Mitsunori Ozaki, Shoya Matsuda,
Masafumi Shoji, Aayako Matsuoka, Yuto Katoh, Yoshizumi Miyoshi and Takahiro Obara

10

The Plasma Wave Experiment (PWE) on board the Arase (ERG) satellite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yoshiya Kasahara, Yasumasa Kasaba, Hirotsugu Kojima, Satoshi Yagitani, Keigo Ishisaka,
Atsushi Kumamoto, Fuminori Tsuchiya, Mitsunori Ozaki, Shoya Matsuda, Tomohiko Imachi,
Yoshizumi Miyoshi, Mitsuru Hikishima, Yuto Katoh, Mamoru Ota, Masafumi Shoji,
Ayako Matsuoka and Iku Shinohara

10

Cover image: Nakamura, Y. et al., Earth, Planets and Space 2018, 70:102 DOI:10.1186/s40623-018-0863-z